Robust second-order tracking of multi-vehicle systems without velocity measurements on directed communication topologies

Second-order consensus tracking problem of uncertain multi-vehicle systems without velocity measurements is studied on the directed communication topologies. We first construct two dynamic controllers via a passivity-based approach for the nominal vehicle model, which are linear and bounded (nonlinear) respectively. We then develop conditions on linear uncertainty and disturbance estimators (UDEs) for the situation having neither velocity measurements nor their asymptotic estimates. Finally, a lowest-order, improved UDE is combined with the two controllers, yielding two robust controllers for the disturbed vehicle model. Numerical simulation cases are presented to show the effectiveness of the controllers.